1. Field of the Invention
The present invention relates to alkaline storage batteries.
2. Description of the Related Art
An enclosed alkaline battery using a battery case often is used as a power source for large scale power, for example, a power source of electric cars or hybrid cars. In such an enclosed alkaline battery; when an electrolyte or a gas component permeates through the battery case and leaks out, the characteristics deteriorate significantly. In order to prevent this leakage, in general, a battery case made of a metal is used.
However, it is difficult to form the battery case made of a metal into an arbitrary shape, and the battery case made of a metal is heavy. On the other hand, although a battery case made of a resin can be processed easily and is light, vapor or oxygen gas or hydrogen gas can permeate through the battery case easily. In particular, in a nickel-metal hydride battery using a hydrogen-absorbing alloy, when the amount of the hydrogen in the battery case is reduced by the hydrogen permeating through the battery case, the capacity balance between the positive electrode and the negative electrode is broken, which may deteriorate the characteristics significantly.
In order to solve this problem, a method for forming a metal layer on the surface of a battery bath made of a resin is proposed (Japanese Patent No. 3049854). However, this method is not preferable, for example, in view of the possibility of short-circuiting because the metal layer is exposed at the surface of the battery case.